Many medical procedures require the ability to accurately navigate medical devices inside the body. In the past, this has been accomplished with mechanically steerable devices. More recently, magnetically navigable medical devices have been developed that can be navigated with an externally applied magnetic field.
However, previously available navigable devices and navigation methods are only marginally acceptable for some procedures where high precision is required. For example, in certain cardiac procedures such as mapping (recording electrical impulses on the surface of the heart); pacing (inducing electrical impulses of the surface of the heart); and ablation (applying RF energy to the heart tissue to ablate the tissue to block stray electrical signals that cause arrhythmias) an electrode must be precisely controlled to contact specific points on the heart. One treatment of cardiac arrhythmias relies upon the formation of a continuous linear lesion from a series of contiguous spot lesions. Such a procedure can be extremely tedious and time consuming with previously available devices and navigation methods.
Examples of mechanically controlled catheters for such procedures include Avitall, U.S. Pat. Nos. 5,354,297, 5,327,905, and 5,642,736; Webster, U.S. Pat. No. Re 34,502; West et al., U.S. Pat. No. 5,318,525; and Webster, Jr., U.S. Pat. No. 5,626,136. These mechanically actuable catheters typically have a limited number of directions of movement. Moreover to navigate the distal end of the catheter to a particular point, the catheter had to be rotated, but rotation of the proximal end of the catheter did not always directly translate to rotation at the distal end, particularly where the path of the catheter was convoluted. Moreover, twists and turns in the catheter would impair or eliminate the ability to control the distal end of the catheter.
Magnets have also been used in such devices. Scheinman, U.S. Pat. No. 5,429,131 and Grayzel, U.S. Pat. No. 4,809,731. However, not for navigation.